1. Field of the Invention
The present invention relates to an automatic air conditioning system with a variable displacement compressor for automotive vehicles, particularly to an automatic air conditioning system with a variable displacement compressor, in which the discharge volume of the compressor is lowered under acceleration conditions only when the evaporator is operated under a cooling condition wherein an intake air temperature, defined by a temperature of air flowing through the evaporator, is lower than a predetermined value, for example a relatively low temperature 5.degree. C.
2. Description of the Prior Disclosure
Recently, there have been proposed and developed various automatic air conditioning systems with a control unit which controls opening angle of doors, such as a switchable fresh/recirculation air intake door, an air mixing door, a defroster door, a chest vent door, a foot vent door, or the like, and controls the amount of air flowing through the evaporator of the air conditioning system in response to output signals from various sensors for detecting various physical quantities, such as an ambient temperature, room temperature in the vehicular cabin, magnitude of insolation, intake air temperature of the evaporator, suction pressure of the compressor, and in response to output signals indicative of ON/OFF state of various switches, such as an air conditioner switch, a blower switch, an ignition switch, a defroster switch, or so forth. In general, under acceleration conditions, such an automatic air conditioning system controls the compressor in such a manner that the discharge volume of refrigerant discharged from the compressor would be lowered regardless of the cooling requirements of the evaporator. Therefore, when an ambient temperature is excessively high, for example during summer days, the cooling power of the compressor may be lowered every time the automotive vehicle is under acceleration. As a result, a relatively warm conditioned air will be discharged from a discharge outlet, such as a chest vent due to the sudden lowering of the cooling power of the compressor. This is unacceptably uncomfortable. Such automatic air conditioning systems have been disclosed in the Japanese Patent First Publication (Tokkai Showa) 59-205553 and the Japanese Utility Model First Publication (Jikkai Showa) 60-152526.